Image forming apparatus, conveyance control method and conveyance control program

Abstract

To suppress deterioration of image quality.SOLUTION: An image forming apparatus comprises: a fixing member; a heating unit that heats the fixing member; a pressing member that is fixed to a main body; an opposing rotary body that contacts the pressing member through the fixing member and forms a nip part between the fixing member and itself; a driving unit that rotationally drives the opposing rotary body or the fixing member; and a conveyance unit that conveys a recording medium having a toner image formed thereon to the nip part. The conveyance unit adjusts timing when the recording medium enters the nip part, on the basis of an amount of toner of a toner image formed on the recording medium.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus, a transport control method, and a transport control program, and more particularly to an image forming apparatus equipped with a fixing device that fixes toner to a recording medium by pressurizing and heating the recording medium, a transport control method executed by the image forming apparatus, and a transport control program that causes a computer to execute the transport control method. [Background technology]

[0002] 2. Description of the Related Art Image forming apparatuses such as copiers, printers, and facsimile machines are provided with a fixing device that applies pressure and heat to a sheet of paper on which a toner image made of toner has been formed, thereby fixing the toner to the sheet of paper.

[0003] For example, Japanese Patent Application Laid-Open No. 2019-120788 describes a fixing device in which, when the cumulative travel distance of the fixing member or the cumulative number of sheets of recording medium passed through exceeds a predetermined value, the heat storage time of the fixing member until the first sheet of recording medium is allowed to enter the fixing nip is set to be longer than the heat storage time of the fixing member until the predetermined value is reached.

[0004] However, a toner image made of toner is formed on the recording medium entering the fixing nip. The toner image formed on the recording medium passing through the fixing device varies depending on the image. Therefore, depending on the toner image formed on the recording medium, the speed at which the fixing device conveys the recording medium may decrease, and the unfixed portion of the toner image formed on the recording medium may come into contact with other components, which may degrade the image quality of the image formed on the recording medium. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-120788 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide an image forming apparatus that suppresses deterioration of image quality.

[0007] Another object of the present invention is to provide a transport control method that suppresses deterioration of image quality.

[0008] Another object of the present invention is to provide a transport control program that suppresses deterioration of image quality. [Means for solving the problem]

[0009] According to one aspect of the present invention, an image forming apparatus includes a fixing member, a heating unit that heats the fixing member, a pressing member fixed to the main body, an opposing rotating body that abuts against the pressing member via the fixing member and forms a nip portion between the fixing member and the opposing rotating body, a drive unit that drives the opposing rotating body or the fixing member to rotate, and a conveying unit that conveys a recording medium on which a toner image has been formed to the nip portion, and the conveying unit adjusts the timing at which the recording medium enters the nip portion based on the amount of toner in the toner image formed on the recording medium.

[0010] According to another aspect of the present invention, a transport control method is a transport control method executed in an image forming apparatus, the image forming apparatus comprising a fixing member, a heating unit that heats the fixing member, a pressing member fixed to a main body, an opposing rotating body that abuts against the pressing member via the fixing member and forms a nip portion between the fixing member and the pressing member, a drive unit that drives the opposing rotating body or the fixing member to rotate, and a transport unit that transports a recording medium on which a toner image has been formed toward the nip portion, and includes an adjustment step that adjusts the timing at which the recording medium enters the nip portion based on the amount of toner in the toner image formed on the recording medium.

[0011] According to yet another aspect of the present invention, a transport control program causes a computer to execute the transport control method described above. [Brief explanation of the drawings]

[0012] [Figure 1]1 is a first perspective view showing the appearance of a printer according to an embodiment of the invention. [Figure 2] FIG. 2 is a cross-sectional view schematically illustrating an example of the internal configuration of a printer. [Figure 3] FIG. [Figure 4] 5A and 5B are schematic diagrams illustrating the principle of idling of the pressure roller. [Figure 5] 10A and 10B are schematic diagrams for explaining how an image defect occurs; [Figure 6] FIG. 2 is a block diagram illustrating an outline of the hardware configuration of a printer. [Figure 7] FIG. 2 is a diagram illustrating an example of functions of a CPU included in a printer. [Figure 8] FIG. 2 is a block diagram showing an example of detailed functions of a toner amount determination unit. [Figure 9] 10 is a flowchart illustrating an example of the flow of a transport control process. [Figure 10] 10 is a flowchart showing an example of the flow of a transfer start time determination process. [Figure 11] 10A and 10B are diagrams illustrating an example of the relationship between the driving force and sliding resistance of a fixing belt and the number of sheets that can be printed. [Figure 12] FIG. 10 is a diagram showing an example of the relationship between the conveying speed of the fixing device and the number of sheets that can be used; [Figure 13] FIG. 10 is a diagram illustrating an example of an extension time table. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same components are designated by the same reference numerals. The names and functions of these components are also the same. Therefore, detailed description thereof will not be repeated.

[0014] FIG. 1 is a first oblique view showing the exterior of a printer according to one embodiment of the invention. FIG. 2 is a cross-sectional view that schematically shows an example of the internal configuration of a printer. For the sake of explanation, the left-right direction in FIG. 2 will be referred to as the left-right direction, and the front-to-back direction will be referred to as the depth direction. The direction from left to right in the left-to-right direction will be referred to as the right-side direction, and the direction from right to left will be referred to as the left-side direction. The direction from front to back in the depth direction will be referred to as the front direction, and the direction from back to front will be referred to as the back direction.

[0015] 1 and 2, printer 100 is an example of an image forming apparatus, and includes an image forming unit 140 for forming an image on a recording medium based on image data, and a paper feed unit 150 for supplying the recording medium to image forming unit 140. The recording medium includes paper and OHP (Over Head Projector) sheets. Here, a case where paper is used as an example of the recording medium will be described.

[0016] The image forming section 140 includes image forming units 20Y, 20M, 20C, and 20K for yellow, magenta, cyan, and black, respectively. Here, "Y," "M," "C," and "K" represent yellow, magenta, cyan, and black, respectively. Print data for yellow, magenta, cyan, and black is input to the image forming units 20Y, 20M, 20C, and 20K, respectively. Since the image forming units 20Y, 20M, 20C, and 20K differ only in the color of the toner they handle, the following description will focus on the image forming unit 20Y for forming yellow images.

[0017] The image forming unit 20Y includes an exposure device 21Y, a photosensitive drum 23Y, a charging roller 22Y, a developing device 24Y, a primary transfer roller 25Y, a toner bottle 41Y, and a toner hopper 42Y. Yellow printing data is input to the exposure device 21Y. The photosensitive drum 23Y is an image carrier. The charging roller 22Y uniformly charges the surface of the photosensitive drum 23Y. The developing device 24Y forms a toner image on the photosensitive drum 23Y. The primary transfer roller 25Y transfers the toner image formed on the photosensitive drum 23Y onto the intermediate transfer belt 30, which is also an image carrier, by the action of an electric field. The drum cleaning blade 27Y removes toner remaining on the photosensitive drum 23Y.

[0018] The toner bottle 41Y contains yellow toner. The toner bottle 41Y is driven by a toner bottle motor to rotate and discharge toner to the outside. The toner discharged from the toner bottle 41Y is supplied to the toner hopper 42Y. The toner hopper 42Y supplies toner to the developing device 24Y when the remaining amount of toner contained in the developing device 24Y falls below a predetermined lower limit.

[0019] Around the photosensitive drum 23Y, a charging roller 22Y, an exposure device 21Y, a developing device 24Y, a primary transfer roller 25Y, and a drum cleaning blade 27Y are arranged in this order along the rotation direction of the photosensitive drum 23Y.

[0020] After being charged by the charging roller 22Y, the photosensitive drum 23Y is irradiated with laser light emitted by the exposure device 21Y. The exposure device 21Y exposes an image-corresponding portion of the surface of the photosensitive drum 23Y to light to form an electrostatic latent image. The developing device 24Y develops the electrostatic latent image formed on the photosensitive drum 23Y with charged toner. Specifically, toner is placed on the electrostatic latent image formed on the photosensitive drum 23Y by the action of electric field force, thereby forming a toner image on the photosensitive drum 23Y. The toner image formed on the photosensitive drum 23Y is transferred onto the intermediate transfer belt 30, which is an image carrier, by the action of electric field force using the primary transfer roller 25Y. Any toner remaining on the photosensitive drum 23Y that has not been transferred is removed from the photosensitive drum 23Y by the drum cleaning blade 27Y.

[0021] Meanwhile, the intermediate transfer belt 30 is suspended by a drive roller 33 and a driven roller 34 so as not to slacken. When the drive roller 33 rotates counterclockwise in FIG. 2, the intermediate transfer belt 30 rotates counterclockwise in the drawing at a predetermined speed. As the intermediate transfer belt 30 rotates, the driven roller 34 rotates counterclockwise.

[0022] As a result, the image forming units 20Y, 20M, 20C, and 20K sequentially transfer toner images onto the intermediate transfer belt 30. The timing at which each of the image forming units 20Y, 20M, 20C, and 20K transfers a toner image onto the intermediate transfer belt 30 is adjusted by detecting the reference marks on the intermediate transfer belt 30. As a result, yellow, magenta, cyan, and black toner images are superimposed on the intermediate transfer belt 30.

[0023] The toner image formed on the intermediate transfer belt 30 is transferred to paper by the action of electric field force by the secondary transfer roller 26, which is a transfer member. The paper is transported by timing roller 31 to nip portion N2 where the intermediate transfer belt 30 and secondary transfer roller 26 come into contact. The paper with the transferred toner image is transported to fixing device 50, where it is heated and pressurized. This melts the toner and fixes it to the paper. The paper is then ejected to paper output tray 39.

[0024] A belt cleaning blade 28 is provided upstream of the image forming unit 20Y on the intermediate transfer belt 30. The belt cleaning blade 28 removes toner remaining on the intermediate transfer belt 30 that has not been transferred to paper.

[0025] When forming a full-color image, the image forming section 140 drives all of the image forming units 20Y, 20M, 20C, and 20K. When forming a monochrome image, the image forming section 140 drives only one of the image forming units 20Y, 20M, 20C, and 20K. It is also possible to form an image by combining two or more of the image forming units 20Y, 20M, 20C, and 20K. The printer 100 described here uses a tandem system, with image forming units 20Y, 20M, 20C, and 20K each forming four colors of toner on paper. The printer 100 may also use a four-cycle system, in which a single photosensitive drum sequentially transfers the four colors of toner onto paper.

[0026] The paper feed unit 150 includes a paper feed cassette 35. A plurality of sheets of paper are set in the paper feed cassette 35. The sheets stored in the paper feed cassette 35 are supplied one by one to the transport path 45 by a take-out roller 36 attached to the paper feed cassette 35, and are sent to the timing rollers 31 by a paper feed roller 37. In addition, one or more sheets of paper may be set in the manual feed cassette 35A. The one or more sheets of paper set in the manual feed cassette 35A are supplied one by one to the transport path 45 by a take-out roller 36A attached to the manual feed cassette 35A. The sheets are then sent to the timing rollers 31 by the paper feed rollers 37.

[0027] FIG. 3 is a front view of the fixing device. FIG. 3 is a view of fixing device 50 as seen from the front. Referring to FIG. 3, fixing device 50 includes heating section 51 and pressure roller 59. Pressure roller 59 is composed of a core metal, an intermediate layer, and a surface layer. In this embodiment, pressure roller 59 has an outer diameter of 30 mm. The core metal is made of aluminum or iron, and the thickness of the core metal is 2 to 3 mm. The intermediate layer is an elastic layer, and is formed from a heat-resistant and elastic material such as silicone rubber or silicone sponge. The thickness of the intermediate layer is preferably about 2 to 5 mm. The surface layer is formed from a material with releasability, such as a fluorine tube, and the thickness of the surface release layer is preferably about 20 to 80 μm.

[0028] The heating unit 51 includes a heating roller 53, a pad member 63, a grease application unit 65, and an endless fixing belt 57. The fixing belt 57 is composed of a base layer and an elastic layer. The base layer is composed of a polyimide film with an inner diameter of 40 mm, a width of 340 mm, and a thickness of 70 μm. The elastic layer is preferably made of silicone rubber and has a thickness of approximately 100 to 150 μm, and the surface layer is made of PFA or PTFE, which has mold-releasability, and is a coating with a thickness of approximately 30 μm. The surface layer is formed by coating the elastic layer with a fluororesin.

[0029] Heat roller 53 is a hollow cylindrical member, and its rotation shaft is supported by the main body case. Heat roller 53 houses heat source 61. The inner diameter of heat roller 53 is set to a size that prevents heat source 61 from coming into contact with it. Heat roller 53 is made of stainless steel. Because heat roller 53 is made of stainless steel, it is strong and easy to process. In this case, the thickness of heat roller 53 can be approximately 0.1 mm to 0.2 mm. Heat roller 53 may also be made of aluminum. In this case, the thickness of heat roller 53 is preferably 0.25 mm or more to ensure strength against bending and local deformation. Heat roller 53 may also be made of an iron-based metal such as STKM (carbon steel pipe for mechanical structures).

[0030] Heat source 61 is, for example, a halogen heater. In this embodiment, two halogen heaters with different light-emitting lengths are used as heat source 61. Note that heat source 61 is not limited to a halogen heater, and a resistance heating element or IH (Induction Heating) may also be used.

[0031] Heat source 61 generates heat, which heats heating roller 53, causing the temperature of heating roller 53 to rise. Thermistor 91 detects the temperature of heating roller 53. Heat source 61 is controlled to be turned on or off depending on the temperature detected by thermistor 91, so that heating roller 53 is controlled to reach a predetermined temperature. By thinning heating roller 53, the thermal capacity of heating roller 53 is reduced. This increases the rate at which the temperature of heating roller 53 rises, shortening the warm-up time required for heating roller 53 to reach a predetermined temperature. In addition, the power consumption of heat source 61 can be reduced.

[0032] The pad member 63 is supported by the support portion 55. The support portion 55 is fixed to the main body frame at both ends. The pad member 63 is made of a heat-resistant resin material. The grease application portion 65 accumulates grease, which is a lubricant, and applies grease to the fixing belt 57 at the portion that comes into contact with the fixing belt 57.

[0033] Heating roller 53, pad member 63, and grease applicator 65 are arranged inside fixing belt 57. Fixing belt 57 is suspended by heating roller 53, pad member 63, and grease applicator 65 so as not to slacken. Therefore, the orbit of fixing belt 57 is determined by heating roller 53, pad member 63, and grease applicator 65.

[0034] A pad member 63 is provided facing the pressure roller 59, and the pad member 63 has a pressing portion 73 that forms a nip portion N1 with the pressure roller 59. The pressure roller 59 is urged toward the pressing portion 73 with a predetermined pressing force. The nip portion N1 is the portion where the fixing belt 57 comes into contact with the pressure roller 59, between the pressing portion 73 and the pressure roller 59. Here, the direction parallel to the rotation axis of the pressure roller 59 is referred to as the longitudinal direction.

[0035] The pressure roller 59 is rotated by a drive motor. As the pressure roller 59 rotates, the fixing belt 57 rotates due to frictional force received from the pressure roller 59 at the contact portion thereof. The fixing belt 57 revolves around the heating roller 53, the pad member 63, and the grease application unit 65. As the fixing belt 57 rotates, the fixing belt 57 rotates due to frictional force received from the fixing belt 57 at the contact portion thereof. Alternatively, the fixing roller 53 may not rotate, and the fixing belt 57 may slide on the surface of the fixing roller 53. The fixing belt 57 revolves around the heating roller 53, the pad member 63, and the grease application unit 65. The fixing belt 57 is heated to a predetermined temperature by heat transferred from the heating roller 53 while in contact with the heating roller 53.

[0036] While the fixing belt 57 passes through the grease application section 65, grease is applied to the inner surface of the fixing belt 57 due to friction between the fixing belt 57 and the grease application section 65. As a result, the frictional resistance that the fixing belt 57 receives from the pad member 63 while passing through the pad member 63 can be made smaller than when grease is not applied.

[0037] The pressing portion 73 of the pad member 63 has a shape that approximates the curvature of the pressure roller 59. This allows the area of ​​the nip portion N1 to be maximized while minimizing the amount of elastic deformation of the pressure roller 59. The increased area of ​​the nip portion N1 allows for a longer time for pressing and heating the paper. Furthermore, the outer diameter of the pressure roller 59 can be reduced to a predetermined value or less, allowing for a more compact fixing device 50. Furthermore, the reduced amount of elastic deformation of the pressure roller 59 allows for a reduced pressing force for pressing the pressure roller 59. Therefore, the strength of the pressure roller 59 can be reduced to a predetermined value or less, allowing for a reduced thickness of the pressure roller 59 and a reduced thermal capacity. Furthermore, the reduced thermal capacity of the pressure roller 59 reduces power consumption.

[0038] A sliding sheet 79 is fixed to the pressing portion 73 of the pad member 63. The sliding sheet 79 is made of heat-resistant glass cloth coated with fluororesin, and is heat-resistant, wear-resistant, and has sliding properties. The fixing belt 57 comes into contact with the sliding sheet. This increases the sliding properties of the surface of the pressing portion 73, thereby minimizing wear of the fixing belt 57 due to friction.

[0039] The sheet of paper Pa carrying the toner To on its surface is guided by guide plate 93 and transported from the bottom to the top of fixing device 50, and passes through nip portion N1. While passing through nip portion N1, the sheet of paper Pa is heated and pressurized by pressure roller 59 and heating portion 51, and the toner To is fixed to the sheet of paper Pa.

[0040] FIG. 4 is a schematic diagram illustrating the principle of idling of the pressure roller. Referring to FIG. 4, the contact state between the pressure roller 59 and the fixing belt 57 is shown for three cases: when the toner amount is low, when it is medium, and when it is high. When the toner amount is medium, a toner image is formed on the paper with a uniform amount of toner of one color across the entire surface of the paper. The toner image has one layer. When the toner amount is high, two toner images are formed on the paper with a uniform amount of toner of two colors across the entire surface of the paper, with two toner images superimposed on each other. The toner image has two layers. When the toner amount is low, a sheet of paper Pa exists between the pressure roller 59 and the fixing belt 57. The sheet of paper Pa contains moisture W, but the moisture W evaporates when heated by the fixing belt 57. Therefore, the moisture W contained in the sheet of paper Pa has little effect on the frictional force between the pressure roller 59 and the sheet of paper Pa.

[0041] When the amount of toner is medium, a sheet of paper Pa carrying toner To is present between the pressure roller 59 and the fixing belt 57. A film of toner To is formed on the surface of the sheet of paper Pa facing the fixing belt 57. The film formed by the toner To prevents the moisture W contained in the sheet of paper Pa from evaporating, and some of it remains without evaporating. As a result, a film of moisture W is formed between the pressure roller 59 and the sheet of paper Pa, reducing the frictional force between the pressure roller 59 and the sheet of paper Pa.

[0042] When the toner amount is large, paper Pa carrying toner To is present between pressure roller 59 and fixing belt 57. The amount of toner To is large compared to when the toner amount is medium. A film of toner To is formed on the surface of paper Pa facing fixing belt 57. The film thickness of toner To is thicker compared to when the toner amount is medium. Therefore, the moisture W contained in paper Pa is prevented from evaporating by the film formed by toner To. Therefore, the film thickness formed by moisture W is thicker compared to when the toner amount is medium. Therefore, the frictional force between pressure roller 59 and paper Pa decreases by a larger amount compared to when the toner amount is medium.

[0043] FIG. 5 is a schematic diagram illustrating the occurrence of an image defect. Referring to FIG. 5, a state in which paper Pa is gripped between nip portions N1 and N2 is shown. Nip portion N1 is a portion between pressing portion 73 and pressure roller 59 where fixing belt 57 and pressure roller 59 come into contact. Nip portion N2 is a portion between drive roller 33 and secondary transfer roller 26 where intermediate transfer belt 30 and secondary transfer roller 26 come into contact. Grease is applied to fixing belt 57 by grease application portion 65. The lower the temperature of fixing belt 57, the higher the viscosity of the grease, and the greater the frictional force between fixing belt 57 and pressing portion 73. In this case, pressure roller 59 rotates idly, slowing down rotation speed V1 of fixing belt 57.

[0044] Meanwhile, because drive roller 33 rotates at a constant rotational speed, the speed V2 at which the paper passes through nip N2 is constant. As a result, the length of the portion of paper Pa located between nip N1 and nip N2 increases, causing paper Pa to curve. This causes paper Pa to come into contact with cover 80, which covers fixing device 50. Before paper Pa passes through nip N1, the toner image is not yet fixed to paper Pa. When the surface of paper Pa on which the toner image has been formed comes into contact with cover 80, the toner image is destroyed in the portion of the toner image that comes into contact with cover 80 and in the surrounding area, resulting in a deterioration in the quality of the image formed on paper Pa. Printer 100 in this embodiment prevents this destruction of the toner image and prevents a deterioration in the quality of the image formed on paper Pa.

[0045] 6 is a block diagram showing an outline of the hardware configuration of the printer 100. Referring to FIG. 6, the printer 100 includes a main circuit 110, a document reading unit 130, an image forming unit 140, a paper feeding unit 150, and an operation panel 160 as a user interface.

[0046] The main circuit 110 includes a CPU (Central Processing Unit) 111 that controls the entire printer 100, a communication interface (I / F) unit 112, a ROM (Read Only Memory) 113, a RAM (Random Access Memory) 114, a hard disk drive (HDD) 115 as a large-capacity storage device, and an external storage device 117. The CPU 111 is connected to the image forming unit 140, the paper feeding unit 150, and the operation panel 160, and controls the entire printer 100.

[0047] The ROM 113 stores programs executed by the CPU 111 or data required to execute the programs. The RAM 114 is used as a work area when the CPU 111 executes the programs.

[0048] The operation panel 160 is provided on the top of the printer 100. The operation panel 160 includes a display unit 161 and an operation unit 163. The display unit 161 is, for example, a liquid crystal display (LCD), and displays an instruction menu for the user, information about acquired image data, and the like. Note that instead of an LCD, any device that displays images, such as an organic EL (electroluminescence) display, can be used.

[0049] The operation unit 163 includes a touch panel 165 and a hard key unit 167. The touch panel 165 is of a capacitance type. Note that the touch panel 165 is not limited to a capacitance type, and other types such as a resistive film type, a surface acoustic wave type, an infrared type, or an electromagnetic induction type can be used. The touch panel 165 has a detection surface that is provided on the upper or lower surface of the display unit 161 and is superimposed on the display unit 161. The hard key unit 167 includes a plurality of hard keys. The hard keys are, for example, contact switches.

[0050] The communication I / F unit 112 is an interface for connecting the printer 100 to a network. The communication I / F unit 112 communicates with other computers or data processing devices connected to the network using communication protocols such as TCP (Transmission Control Protocol) or FTP (File Transfer Protocol). The network to which the communication I / F unit 112 is connected is a local area network (LAN), and the connection type can be either wired or wireless. The network is not limited to a LAN, and can also be a wide area network (WAN), a public switched telephone network (PSTN), the Internet, or the like.

[0051] External storage device 117 is controlled by CPU 111, and is equipped with a CD-ROM (Compact Disk Read Only Memory) 118 or a semiconductor memory. In this embodiment, an example will be described in which CPU 111 executes a program stored in ROM 113. CPU 111 may control external storage device 117 to read a program to be executed by CPU 111 from CD-ROM 118, store the read program in RAM 114, and execute it.

[0052] The recording medium for storing the programs executed by CPU 111 is not limited to CD-ROM 118, but may be a flexible disk, cassette tape, optical disk, IC card, optical card, semiconductor memory, etc. Optical disks include MO (Magnetic Optical Disc), MD (Mini Disc), and DVD (Digital Versatile Disc). Semiconductor memory includes mask ROM and EPROM (Erasable Programmable ROM).

[0053] Furthermore, CPU 111 may load a program stored in HDD 115 into RAM 114 and execute it. The programs stored in HDD 115 include programs downloaded by CPU 111 from a computer connected to the network, and programs written by a computer connected to the network to HDD 115. The programs referred to here include not only programs that can be directly executed by CPU 111, but also source programs, compressed programs, encrypted programs, etc.

[0054] Fig. 7 is a diagram showing an example of functions of a CPU included in a printer. The functions shown in Fig. 7 are realized by CPU 111 included in printer 100 as CPU 111 executes an image forming program stored in ROM 113, HDD 115, or CD-ROM 118. Referring to Fig. 7, CPU 111 includes a print job receiving unit 171, a heating control unit 173, a toner amount determination unit 175, a paper width acquisition unit 177, a cumulative sheet number acquisition unit 179, a heat amount calculation unit 181, and a transport control unit 183.

[0055] The print job receiving unit 171 receives a print job. The print job is input to the printer 100 from an external device. When a user operates a personal computer (PC) connected to the printer 100 via a network to specify image data and set printing conditions, the PC generates a print job. The PC sends the print job to the printer 100. When the communication I / F unit 112 receives the print job from the PC, the CPU 111 receives the print job. The print job receiving unit 171 outputs the print job to the toner amount determination unit 175 and the paper width acquisition unit 177.

[0056] The toner amount determination unit 175 determines the amount of toner based on the image data included in the print job. The toner amount includes coverage and a unit toner amount. The toner amount determination unit 175 determines the amount of toner for an image in the image data at a predetermined distance from the leading edge of the paper Pa in the transport direction. The predetermined distance is the value obtained by subtracting the distance between the nip N1 and the nip N2 from the length of the paper Pa on the transport path 45 for the paper Pa. If the length of the portion of the paper Pa that does not pass through the nip N1, to be fixed by the fixing device 50, is equal to or less than the distance between the nip N1 and the nip N2, the toner image is less likely to come into contact with other portions.

[0057] Fig. 8 is a block diagram showing an example of detailed functions of the toner amount determination unit. Referring to Fig. 8, toner amount determination unit 175 includes a coverage calculation unit 191 and a unit toner amount acquisition unit 193. Toner amount determination unit 175 calculates coverage. Coverage is the ratio of the area of ​​an image formed on a sheet to the area of ​​the sheet. Coverage calculation unit 191 calculates coverage from the number of pixels included in the image data whose pixel values ​​are greater than 0 and the number of pixels included in the image data.

[0058] The unit toner amount obtaining unit 193 calculates the unit toner amount. The unit toner amount is the amount of toner per unit area. The larger the pixel value of the image data, the larger the toner amount. The unit toner amount obtaining unit 193 calculates the unit toner amount from, for example, the average pixel value of the image data.

[0059] 7, toner amount determination unit 175 outputs the toner amount to conveyance control unit 183. When the image data included in the print job includes multiple pages, toner amount determination unit 175 determines the toner amount corresponding to each of multiple sheets of paper on which the images of the multiple pages are formed.

[0060] The paper width acquisition unit 177 acquires the width of the paper on which an image is formed. The print job includes printing condition information that defines the conditions for forming the image. The printing condition information includes the size of the paper. The paper size includes the length of the paper in the width direction. The width direction of the paper is the direction perpendicular to the paper transport direction. The paper width acquisition unit 177 outputs the length of the paper in the width direction to the transport control unit 183.

[0061] The cumulative number acquisition unit 179 acquires the number of sheets of paper that have passed through the fixing device 50 as the cumulative number of sheets. The cumulative number acquisition unit 179 counts the number of sheets of paper on which the printer 100 has formed an image and stores it in the HDD 115. The cumulative number acquisition unit 179 acquires the counted number of sheets of paper from the HDD 115 as the cumulative number of sheets. If the fixing device 50 has been replaced, the cumulative number acquisition unit 179 acquires the cumulative number of sheets since the fixing device 50 was replaced. The cumulative number acquisition unit 179 outputs the cumulative number to the conveyance control unit 183.

[0062] The heating control unit 173 controls the heat source 61 included in the fixing device 50. The heating control unit 173 switches the heat source 61 ON in response to a print job being input to the printer 100. Thereafter, the heating control unit 173 switches the heat source 61 ON and OFF based on the output of the thermistor 91. The heating control unit 173 outputs the time during which the heat source 61 is switched ON after the printer 100 is powered on as the heating time to the heat amount calculation unit 181. The heating control unit 173 also outputs the time during which the heat source 61 is switched OFF after the printer 100 is powered on as the non-heating time to the heat amount calculation unit 181.

[0063] The heat amount calculation unit 181 calculates the amount of heat of the fixing device 50. The heat amount calculation unit 181 calculates the amount of heat of the fixing device 50 based on the heating time and non-heating time input from the heating control unit 173. A table that defines the relationship between the difference between the heating time when the heat source 61 is switched on and the non-heating time when the heat source 61 is switched off and the amount of heat is stored in the HDD 115. The heat amount calculation unit 181 obtains the amount of heat of the fixing device 50 by referring to the table. Furthermore, if the printer 100 is equipped with a temperature sensor that detects the outside air temperature, the heat amount calculation unit 181 may calculate the amount of heat using an arithmetic expression. The heat amount calculation unit 181 outputs the amount of heat of the fixing device 50 to the conveyance control unit 183.

[0064] The transport control unit 183 controls the timing rollers 31 and determines when the timing rollers 31 start transporting the paper. The transport control unit 183 determines the transport start time from when a print job is received until when the timing rollers 31 start transporting the paper. The time from when a print job is received until when the timing rollers 31 start transporting the paper is determined in advance as the normal time and stored in the HDD 115. The normal time may vary depending on the outside temperature at the location where the printer 100 is installed. For this reason, a table or an arithmetic expression that defines the relationship between the outside temperature and the normal time is stored in advance in the HDD 115. For the sake of explanation, the following description will be given using an example where the outside temperature is constant.

[0065] The conveyance control unit 183 determines a shorter normal time value as the heat quantity input from the heat quantity calculation unit 181 increases. The larger the heat quantity of the fixing device 50, the smaller the heat quantity required for the temperature of the fixing belt 57 to reach a predetermined temperature. The smaller the heat quantity of the fixing device 50, the larger the heat quantity required for the temperature of the fixing belt 57 to reach a predetermined temperature.

[0066] The conveyance control unit 183 determines the conveyance start time based on the toner amount input from the toner amount determination unit 175. When the cumulative number of sheets input from the cumulative sheet number acquisition unit 179 is equal to or greater than a predetermined threshold value TH1, the conveyance control unit 183 determines the conveyance start time to be longer than the normal time. When the cumulative number of sheets input from the cumulative sheet number acquisition unit 179 is smaller than the threshold value TH1, the conveyance control unit 183 determines the conveyance start time to be the normal time. The threshold value TH1 is a value derived through experiments or the like as the cumulative number of sheets at which the frictional force between the fixing belt 57 and the pressing unit 73 becomes equal to or less than a predetermined value when the fixing device 50 is heated for the normal time. The threshold value TH1 is stored in advance in the HDD 115.

[0067] The transport control unit 183 determines the transport start time to be a value longer than the normal time as the toner amount input from the toner amount determination unit 175 increases. The transport control unit 183 determines the transport start time to be a value longer than the normal time as the coverage increases. The transport control unit 183 determines the transport start time to be a value longer than the normal time as the unit toner amount increases.

[0068] 9 is a flowchart showing an example of the flow of a transport control process. The transport control process is performed by CPU 111 of printer 100 as CPU 111 executes an image forming program stored in ROM 113, HDD 115, or CD-ROM 118. Referring to FIG. 9, CPU 111 determines whether a print job has been accepted (step S01). CPU 111 waits until communication I / F unit 112 receives a print job from a PC (NO in step S01), and if the print job has been received (YES in step S01), the process proceeds to step S02. In response to the reception of the print job, heat source 61 is turned on, and heating of fixing belt 57 begins.

[0069] In step S02, the amount of toner is determined for each page, and processing proceeds to step S03. The amount of toner is determined for each of one or more pages included in the image data included in the print job. CPU 111 determines the amount of toner for an image in a portion of the page of image data that is a predetermined distance from the leading edge in the transport direction of paper Pa. The predetermined distance is a value obtained by subtracting the distance between nip portion N1 and nip portion N2 from the length of paper Pa on transport path 45 for paper Pa. If the image data includes images of multiple pages, the amount of toner is determined for each of the multiple pages. The toner amount includes coverage and unit toner amount.

[0070] In step S03, the cumulative number of sheets is obtained, and the process proceeds to step S04. The cumulative number of sheets stored in HDD 115 is read. The cumulative number is the total number of sheets on which the fixing device 50 has fixed the toner image. In step S04, the cumulative number of sheets is compared with a threshold value TH1. If the cumulative number of sheets is equal to or greater than the threshold value TH1, the process proceeds to step S05; otherwise, the process proceeds to step S11.

[0071] In step S05, variable n is set to 1, and the process proceeds to step S06. Variable n is information that identifies one or more pages included in the image data. In step S06, page n is selected as the processing target, and the process proceeds to step S07.

[0072] In step S07, the amount of heat is acquired, and the process proceeds to step S08. The amount of heat of the fixing device 50 is acquired. Specifically, the amount of heat is calculated from the accumulated time that the heat source 61 is ON since the printer 100 was powered on and the accumulated time that the heat source 61 is OFF. In step S08, the normal time is determined, and the process proceeds to step S09. The normal time is determined based on the amount of heat acquired in step S07. The normal time is the time it takes for the fixing belt 57 to reach a predetermined temperature. The normal time may be determined by referring to a table stored in HDD 115, or may be determined using an arithmetic expression.

[0073] In step S09, a transfer start time determination process is executed, and the process proceeds to step S10. The details of the transfer start time determination process will be described later, but this process determines the transfer start time. In step S10, it is determined whether the transfer start time has elapsed since the print job was accepted in step S01. The process remains in a standby state until the transfer start time has elapsed since the print job was accepted (NO in step S10), and if the transfer start time has elapsed since the print job was accepted (YES in step S10), the process proceeds to step S11.

[0074] In step S11, CPU 111 starts conveying the paper. CPU 111 drives timing roller 31 to convey the paper. The paper passes through nip portion N2 and is conveyed to fixing device 50. At this stage, heat source 61 heats fixing belt 57 for a time period equal to or longer than the conveyance start time, so the frictional force between fixing belt 57 and pressing portion 73 is reduced. This prevents the conveyance speed of fixing belt 57 from slowing down.

[0075] In step S12, it is determined whether or not there is a page to be imaged next. If there is a page to be imaged next, the process proceeds to step S13; if not, the process ends. In step S13, the variable n is incremented, and the process returns to step S06.

[0076] FIG. 10 is a flowchart showing an example of the flow of the transport start time determination process. The transport time determination process is a process executed in step S09 of the transport control process. Referring to FIG. 10, in step S21, CPU 111 determines a larger value for the transport start time as the coverage increases, and proceeds to step S22. The transport start time is set to a value larger than the normal time. In step S22, CPU 111 determines a larger value for the transport start time as the unit toner amount increases, and proceeds to step S23. The transport start time is set to a value larger than the normal time. In step S23, CPU 111 determines a larger value for the transport start time as the paper width increases, and returns the process to the transport control process. The transport start time is set to a value larger than the normal time.

[0077] <Example> FIG. 11 is a diagram showing an example of the relationship between the driving force and sliding resistance of the fixing belt and the number of sheets that can be printed. Referring to FIG. 11, the horizontal axis represents the number of sheets that can be printed, and the vertical axis represents the driving force and sliding resistance of fixing belt 57. The driving force of fixing belt 57 is the torque of pressure roller 59. Solid line P1 represents the torque of pressure roller 59. Dotted line P2 represents the sliding resistance of fixing belt 57. The sliding resistance of fixing belt 57 is the frictional force between fixing belt 57 and pressing portion 73.

[0078] The number of sheets that can be used is inversely proportional to the driving force of the fixing belt 57. The greater the number of sheets that can be used, the lower the driving force of the fixing belt 57. The number of sheets that can be used is proportional to the sliding resistance of the fixing belt 57. The greater the number of sheets that can be used, the higher the sliding resistance of the fixing belt 57.

[0079] When the frictional force between the pressure roller 59 and the fixing belt 57 becomes smaller than the sliding resistance of the fixing belt 57, the pressure roller 59 rotates freely, reducing the conveyance speed of the paper Pa. Furthermore, when the difference between the frictional force between the pressure roller 59 and the fixing belt 57 and the sliding resistance of the fixing belt 57 becomes equal to or less than a predetermined value, the pressure roller 59 may rotate freely.

[0080] FIG. 12 is a diagram showing an example of the relationship between the conveying speed of the fixing device and the number of sheets that can be used. Referring to FIG. 12, the horizontal axis shows the number of sheets that can be used, and the vertical axis shows the conveying speed of the fixing device 50. The dashed-dotted line P1 shows the conveying speed of blank paper, which is paper on which no toner image is formed. The dotted line P2 shows the conveying speed of paper on which a single-color toner image is formed. The dotted line P3 shows the conveying speed of paper on which a two-color toner image is formed. The number of sheets that can be used is proportional to the conveying speed of the fixing device 50. The greater the number of sheets that can be used, the slower the conveying speed of the fixing device 50. Furthermore, the greater the number of colors in the toner image formed on the paper, the greater the rate of decrease in the conveying speed.

[0081] The amount of reduction in the paper transport speed is calculated using the following formula, weighted by the presence or absence of paper, the presence or absence of toner, and the amount of toner. V0 is the amount of reduction in the transport speed of the fixing device 50 when fixing blank paper. V1 is the amount of reduction in the transport speed of the fixing device 50 when fixing paper on which a single-color toner image is formed. V2 is the amount of reduction in the transport speed of the fixing device 50 when fixing paper on which a two-color toner image is formed. In this case, the relationship ΔVn<ΔV0<ΔV1<ΔV2 holds. The transport speeds Vn, V0, V1, and V2 are determined in advance by experiment, etc. Also, the width L of the fixing belt 57, the width L0 of the paper, the width L1 of the single-color toner image, and the width L2 of the two-color toner image are defined. The width L of the contact area between the pressure roller 59 and the fixing belt 57 is defined. The amount of reduction is calculated using the following formula (1). Decrease amount = (ΔV0×L0+ΔV1×L1+ΔV2×L2) / L … (1) Based on the amount of decrease calculated using formula (1), an extension time for extending the transport start time beyond the normal time can be determined.

[0082] FIG. 13 is a diagram showing an example of an extension time table. Referring to FIG. 9, the extension time table defines an extension time for a combination of toner amount and paper width. The toner amount indicates a value obtained by multiplying coverage by the unit toner amount. Extension times are defined for cases where the normal time is less than 60 seconds and cases where the normal time is 60 seconds or more. For example, for a combination of a toner amount of 150% or more but less than 200% and a paper width of 297 mm, an extension time of 12 seconds is defined when the normal time is less than 60 seconds, and an extension time of 5 seconds is defined when the normal time is 60 seconds or more.

[0083] If this extension time table is stored in the HDD 115, the CPU 111 refers to the extension time table to determine the transport start time.

[0084] <Other variations> (1) In this embodiment, an example is shown in which heat from the heating roller 53 is transferred by conduction to heat the fixing belt 57. However, radiant heat emitted from the heating roller 53 may also be used to heat the fixing belt 57. In this case, the fixing belt 57 and the heating roller 53 do not need to come into contact with each other. Therefore, the fixing belt 57 does not need to be suspended by the heating roller 53, the pad member 63, and the grease application unit 65. Specifically, the fixing belt 57 is pressed between the pad member 63 and the pressure roller 59 and is supported by the pad member 63 and the pressure roller 59. Furthermore, the fixing belt 57 slides against the pad member 63 as the pressure roller 59 rotates. This causes the fixing belt 57 to rotate around the pad member 63.

[0085] (2) The heating roller 53 may also be disposed outside the fixing belt 57. In this case, the fixing belt 57 rotates around the pad member 63. The heating roller 53 does not need to be cylindrical, and an induction heater or a ceramic heater that functions as a heat source may be used.

[0086] (3) In this embodiment, the pressure roller 59 is pressed against the pad member 63 , but the pad member 63 may be pressed against the pressure roller 59 .

[0087] (4) In the present embodiment, the pressure roller 59 is driven and the fixing belt 57 is rotated by the pressure roller 59. However, the pressure roller 59 may be rotated by the fixing belt 57. In this case, a motor for rotating the heating roller 53 is provided.

[0088] (5) In the present embodiment, an example has been shown in which the pressure roller 59 is pressed against the fixing belt 57. However, the pressure roller 59 may be separated from the fixing belt 57 while the fixing device 50 is not in operation. Preferably, the pressure roller 59 is pressed against the heating unit 51 at least while the paper passes through the nip portion N1. This makes it possible to limit the period during which the pressure roller 59 is elastically deformed while the paper passes through.

[0089] (6) In this embodiment, the printer 100 has been described as an example of an image forming device, but the image forming device may also be a copier, a laser beam printer, a facsimile machine, or a multifunction peripheral (Multi Function Peripheral) that combines these.

[0090] (7) In the present embodiment, a tandem printer 100 that forms color images has been described as an example of an image forming apparatus. However, the present invention is not limited to this, and may be an image forming apparatus that forms monochrome images. The configurations and arrangements of the image forming units 20Y, 20M, 20C, and 20K, the secondary transfer roller 26, and the fixing device 50 are not limited to those of the present embodiment, and other configurations and arrangements may be used.

[0091] <Summary of implementation form> (Item 1) a fixing member; a heating section that heats the fixing member; a pressing member fixed to the main body; a counter rotating body that contacts the pressing member via the fixing member and forms a nip portion between the fixing member and the pressing member; a driving unit that drives the opposing rotating body or the fixing member to rotate; a conveying section that conveys the recording medium on which the toner image is formed to the nip section, The conveying section adjusts the timing at which the recording medium enters the nip section based on the amount of toner in the toner image formed on the recording medium.

[0092] According to this aspect, the counter rotor contacts the pressing member via the fixing member, forming a nip between the fixing member and the counter rotor. A recording medium on which a toner image is formed is transported toward the nip. The driving unit rotates the counter rotor or the fixing member. Therefore, the fixing member contacts the counter rotor directly or indirectly via the recording medium at the nip, and slides against the pressing member fixed to the main body while the driving unit rotates the counter rotor or the fixing member. The timing at which the recording medium enters the nip is adjusted based on the amount of toner in the toner image formed on the recording medium. The recording medium can enter the nip after the frictional force generated when the fixing belt slides against the pressing member is reduced. This prevents the counter rotor from spinning freely relative to the fixing member or the fixing member from decreasing in rotational speed, allowing the recording medium to be transported at a predetermined speed and preventing the toner image from coming into contact with other members before being fixed to the recording medium. As a result, an image forming apparatus can be provided that suppresses degradation of image quality.

[0093] (Item 2) The image forming apparatus according to item 1, wherein the toner amount includes a ratio of the toner image to the surface of the paper on which the toner image is formed.

[0094] According to this aspect, the timing at which the recording medium enters the nip portion is adjusted based on the ratio of the toner image to the surface of the recording medium on which the toner image is formed. There is a predetermined relationship between the ratio of the toner image to the surface of the recording medium on which the toner image is formed and the frictional force between the opposing rotor and the recording medium. When the opposing rotor is rotated, idling of the opposing rotor relative to the fixing member can be suppressed.

[0095] (Item 3) The image forming apparatus according to item 1 or 2, wherein the toner amount includes an amount per unit area.

[0096] According to this aspect, the timing at which the recording medium enters the nip portion is adjusted based on the amount of toner per unit area. There is a predetermined relationship between the amount of toner per unit area and the frictional force between the opposing rotating body and the recording medium. When the opposing rotating body is rotated, idling of the opposing rotating body relative to the fixing member can be suppressed.

[0097] (Item 4) The image forming apparatus according to any one of items 1 to 3, wherein the transport unit adjusts the timing at which the recording medium enters the nip portion based on the length of the recording medium in a direction intersecting the transport direction.

[0098] According to this aspect, the timing at which the recording medium enters the nip portion is adjusted based on the length of the recording medium in a direction intersecting the conveyance direction. The longer the length of the recording medium in a direction intersecting the conveyance direction, the smaller the contact area between the opposing rotor and the fixing member. There is a predetermined relationship between the contact area and the frictional force generated at the contact point between the opposing rotor and the fixing member. Therefore, when the opposing rotor is driven to rotate, idling of the opposing rotor relative to the fixing member can be suppressed.

[0099] (Item 5) An image forming apparatus according to any one of items 1 to 4, wherein the transport section adjusts the timing at which the recording medium enters the nip section based on the amount of toner in the toner image formed at a predetermined distance from the leading edge of the recording medium in the transport direction.

[0100] According to this aspect, the timing at which the recording medium enters the nip is adjusted based on the amount of toner in the toner image formed in a portion of the recording medium a predetermined distance from the leading edge in the conveyance direction. After the portion of the recording medium that is a predetermined distance from the leading edge passes through the nip, the probability that the toner image formed in the portion of the recording medium that has not passed through the nip will come into contact with other components is low. This reduces the load of the process of calculating the toner amount.

[0101] (Item 6) An image forming apparatus according to any one of items 1 to 5, wherein the transport section does not adjust the timing at which the recording medium enters the nip section when the number of the recording media passing through the nip section is equal to or less than a predetermined value.

[0102] According to this aspect, when the number of recording media passing through the nip portion is equal to or less than a predetermined value, the timing at which the recording media enter the nip portion is not adjusted. Therefore, the timing at which the recording media enter the nip portion is not adjusted until the frictional force between the fixing member and the sliding portion becomes large, which simplifies the process.

[0103] (Item 7) In the image forming apparatus according to any one of Items 1 to 6, the transport section determines the timing at which the recording medium enters the nip section based on the total heat quantity of the fixing member.

[0104] According to this aspect, the timing at which the recording medium enters the nip portion is determined based on the heat quantity of the fixing member. There is a correlation between the heat quantity of the fixing member and the frictional force between the fixing member and the fixed member. Therefore, the timing at which the recording medium enters the nip portion can be accurately determined.

[0105] (Section 8) A transport control method executed in an image forming apparatus, The image forming apparatus includes a fixing member and a heating section that heats the fixing member; a pressing member fixed to the main body; a counter rotating body that contacts the pressing member via the fixing member and forms a nip portion between the fixing member and the pressing member; a driving unit that drives the opposing rotating body or the fixing member to rotate; a conveying section that conveys the recording medium on which the toner image is formed toward the nip section, A transport control method comprising: adjusting a timing at which the recording medium enters the nip portion based on an amount of toner in the toner image formed on the recording medium.

[0106] According to this aspect, it is possible to provide an image forming method that suppresses deterioration of image quality.

[0107] (Item 9) A transport control program that causes a computer to execute the transport control method according to Item 8.

[0108] According to this aspect, it is possible to provide an image forming program that suppresses deterioration of image quality.

[0109] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0110] 100 printer, 20Y, 20M, 20C, 20K image forming unit, 21Y exposure device, 22Y charging roller, 23Y photosensitive drum, 24Y developing device, 25Y primary transfer roller, 26 secondary transfer roller, 30 intermediate transfer belt, 31 timing roller, 33 drive roller, 34 driven roller, 45 transport path, 50 fixing device, 51 heating unit, 53 heating roller, 55 support unit, 57 fixing belt, 59 pressure roller, 61 heat source, 63 pad member, 65 grease application unit, 73 pressing unit, 79 sliding sheet, 80 cover, 91 thermistor, 111 CPU, 112 communication I / F unit, 113 ROM, 114 RAM, 115 HDD, 117 external storage device, 118 CD-ROM, 140 image forming unit, 171 Print job receiving unit, 173 heating control unit, 175 toner amount determination unit, 177 paper width acquisition unit, 179 cumulative number acquisition unit, 181 heat amount calculation unit, 183 conveyance control unit, 191 coverage calculation unit, 193 unit toner amount acquisition unit, N1, N2 nip unit, Pa paper, To toner, W moisture.

Claims

1. A fixing member; a heating section that heats the fixing member; a pressing member fixed to the main body; a counter rotating body that contacts the pressing member via the fixing member and forms a nip portion between the fixing member and the pressing member; a driving unit that drives the opposing rotating body or the fixing member to rotate; a conveying section that conveys the recording medium on which the toner image is formed to the nip section; a conveyance control unit that adjusts the timing at which the recording medium enters the nip portion based on the amount of toner in the toner image formed on the recording medium.

2. 2. The image forming apparatus according to claim 1, wherein the toner amount includes a ratio of the toner image to the surface of the recording medium on which the toner image is formed.

3. The image forming apparatus according to claim 1 , wherein the toner amount includes an amount per unit area.

4. The image forming apparatus according to claim 1 , wherein the transport control unit adjusts the timing at which the recording medium enters the nip portion based on the length of the recording medium in a direction intersecting the transport direction.

5. 2. The image forming apparatus according to claim 1, wherein the transport control unit adjusts the timing at which the recording medium enters the nip portion based on the amount of toner in the toner image formed at a predetermined distance from the leading edge of the recording medium in the transport direction.

6. 2. The image forming apparatus according to claim 1, wherein the transport control unit does not adjust the timing at which the recording media enter the nip portion when the number of the recording media passing through the nip portion is equal to or less than a predetermined value.

7. 7. The image forming apparatus according to claim 1, wherein the transport control section determines the timing at which the recording medium enters the nip section based on the amount of heat of the fixing member.

8. A transport control method executed in an image forming apparatus, The image forming apparatus includes a fixing member and a heating section that heats the fixing member; a pressing member fixed to the main body; a counter rotating body that contacts the pressing member via the fixing member and forms a nip portion between the fixing member and the pressing member; a driving unit that drives the opposing rotating body or the fixing member to rotate; a conveying section that conveys the recording medium on which the toner image is formed toward the nip section, A transport control method comprising: adjusting a timing at which the recording medium enters the nip portion based on an amount of toner in the toner image formed on the recording medium.

9. A transport control program that causes a computer to execute the transport control method according to claim 8.

Images